In this article, we would like to address the topic of wood drying and storage.

1. What do ‘air-dried’ and ‘artificially dried’ mean?

We offer air-dried and artificially dried products. After cutting, we first dry the wood very carefully and gently in the fresh air. This type of drying is a very slow process, so it can take years before the wood is suitable for further processing. In addition, it does not dry any further than the ambient humidity, which is between 15 and 20% in our latitudes. Air-dried wood is therefore more suitable for outdoor use.

Our artificially dried wood is mostly used indoors. Due to the reduced moisture content, it is less prone to warping or cracking, although such defects can never be completely ruled out with wood as a natural product.

We dry 80% of our wood stocks in a vacuum drying chamber. Before this happens, the wood must first be left to dry in the air for up to two years after being cut. This slow and gentle drying process is crucial for quality. We call this process pre-drying.

Once the moisture content of the wood has fallen sufficiently, it is dried in the drying chamber using vacuum and temperature to a final moisture content of 10-12%.
This type of artificial drying has many advantages. The vacuum allows the water to escape from the wood more gently than with conventional fresh air/exhaust air dryers, as good drying results can be achieved at lower temperatures. We also have the option of using buffer storage tanks to collect the heat generated and reuse it.
When drying, harder and therefore denser types of wood require a longer drying time to achieve the desired residual moisture content than softer types of wood. If drying is too rapid, there is a risk of cracking or cell collapse.

2. Wood is hygroscopic!

Wood can also absorb moisture again! Once dry does not always mean dry!
Wood is hygroscopic, which means that it can absorb and release moisture to a certain extent. The moisture content can therefore fluctuate even after years and even in artificially dried wood. For example, due to the change of seasons.
The absorption of moisture is referred to as swelling, while the release of moisture is referred to as shrinkage. This does not happen in a short period of time, but when the climate is constant for a while, it slowly adapts and absorbs or releases moisture.

3. Structure of the wood cell structure in context

The first illustration shows the cell structure of a living tree, with the cell walls and cell cavities “filled” with water. The water content here is over 60%. Figure 2 clearly shows that the water content in the cell cavities decreases. Once the cavities no longer contain any water (only the cell walls), this is referred to as the fiber saturation point. If the wood continues to dry, it begins to shrink. In the third illustration, the cell walls are partially dry. This corresponds to air-dried wood, which is around 15%. If the wood is dried to almost 0%, it is referred to as kiln-dried.

4. How should wood be stored correctly?

Depending on whether the wood is air-dried or artificially dried, it should be stored under a roof or indoors, for example in a dry workshop. A damp garage or shed is therefore not suitable for storing high-quality wood.

However, it always depends on the type of wood: there are particularly sensitive types of wood for which even slight temperature fluctuations are enough to cause problems, such as cracking.

When purchasing wood, please ask us how exactly each type of wood should be stored.
Freshly cut wood should always be stored in a well-ventilated area, but without drafts. In addition, never place cold wood in a warm room or workshop, or near a heater, as it will crack!